The food could make her smelly if it has a lot of grain in it, but really, what kind of smell are you talking about? Yeast infections have a nasty smell, as do plain old ear infections. Have you had a look down in her ears? What are you feeding her?
I feed her Beneful weight control. She doesn't have an ear infection they look clean. The smell is kind of a dirty wet dog smell kind of stale, and seams to originate from her backside. She is an indoor dog and goes to work with me everyday. The only thing I have changed in the last few weeks is her food.